Adaptor for cutout base receptacles



Feba 7, 1950 w. Q EDSALL 2,496,662

ADAPTER FOR CUTOUT BASE RECEPTACLES vFiled. Sept. 11, 1947 www Patented Feb. 7, 1950 ADAPTOR FOR CUTOUT BASE RECEPTACLES William S. Edsall, Cambridge, Mass., assgnor to The Chase-Shawmut Company, Newburyport, Mass., a corporation of Massachusetts Application September 11, 1947, Serial No. 773.367 i (Cl. ZOO-119) 4 Claims.

This invention relates to improvements in tamper-resisting cut-outs of the fuse plug type wherein an adapter device may be mounted in a cut-outs base receptacle for coaction with a fuse plug to make it diiiicult to restore a circuit through the assembly, following an interruption of the circuit by the fuse plug, excepting by replacing the blown fuse plug by a new one. More particularly, the invention provides improvements in the adapters for such cut-outs of the general type disclosed in the co-pending application of Elmer H. Taylor, Serial No. 697,662, my present invention providing means whereby the adapters are capable of coaction with a plurality of types of fuse plugs, one of which types is adapted for operative mounting in a cut-out base receptacle both with and without the adapter in the receptacle,

Fuse-tampering long has been recognized as a serious problem in the electrical industry, and numerous proposals have been directed toward making it diicult to complete a circuit through a fuse plug whose fusible element or other cutout mechanism has interrupted the circuit in response to overload. The hazards created by A the all to prevalent practices of inserting a penny, or tinfoil, or other foreign conducting means, in a cut-out base receptacle in order to complete a circuit through a blown fuse plug are of such a serious nature that those charged with the responsibility oi' preparingI the National Electrical Code have deemed it necessary to include provisions making it mandatory in all new installations to employ tamper-resisting fuse plugs and adapters approved or to be approved by the committee responsible .for the enforcement of the code. The so-called type S fuse plug and adapter unit has been approved by the code committee and presently is being supplied to the trade. The said type S plug and adapter unit ts any standard Edison base receptacle so that it is suitable for the base receptacles heretofore installed as well as those being installed in new construction. f

However, the said type S fuse plug is not usable without its adapter in the standard Edison base receptacle, and there has been a strenuous and persistent demand in the industry, particularly by public utilities and other large users of fuses, that tamper-resisting fuse plugs should be usable in the standard Edison base receptacles either with or without adapters. Such a fuse plug and adapter unit has been developed which meets the said urgent demand for a plug and adapter unitgwhose fuse plug maybe used in the stand ard Edison base receptacle either with or without the adapter in the receptacle.

Also, it is desirable that tamper-resisting fuse plugs, when operatively mounted in a base receptacle, shall project out of the receptacle not appreciably more than conventional fuse plugs.` This is important because a large percentage of presently installed base receptacles are enclosed in fuse boxes whose covers, when closed, provide only a slight clearance between a conventional fuse plug and cover. Hence, if an adapter requires an associated fuse plug to project out of a base receptacle substantially more than a conventional fuse plug, as is the case with the said type S fuse plug and adapter unit, the fuse box covers engage the fuse plugs and are prevented from closing.

It is among the objects of my present invention to provide an adapter for standard Edison base cut-out receptacles which can accommodate inter-changeably both the said type S fuse plug and the mentioned fuseplug which is usable either with or without an adapter in the standard Edison base receptacle. My improved adapter comprises an insulating sleeve having a threaded axial hole therethrough in which the exteriorly threaded center-contact-carrying portion of said type S fuse plug may be screwed to engage lits center contact directly with the center contact of the base receptacle, and through which the non-threaded center-contact-carrying portion of the other mentioned type of fuse plug may pass to similarly engage its center contact directly with the center contact of the base recepacle, the adapter having means thereon for effecting electrical connection between the screw shell contact of the base receptacle and the screw shell contact of whichever type of fuse plug is mounted in the receptacle,

Another object is to provide an adapter for standard Edison base cut-out receptacles having provision for accommodating any one of a plurality of types of tamper-resisting fuse plugs with the center contact of whichever type of fuse plug is embodied in the receptacle directly engaged with the center contact of the base receptacle, whereby the tamper-resisting fuse plug will project out of the receptacle substantially the same amount as conventional fuse plugs regardless of which of the plurality of tamperf resisting fuse plugs is mounted in the receptacle.

A further object is to provide an adapter for standard Edison base cut-out receptacles wherein provision is made for passage through the adapter of the center contact of either of a plu-y rality of types of fuse plugs into direct engagement with the center contact of the base receptacle, and wherein means is provided for elec trical connection of the screw shell contact o the base receptacle with the screw shell contact of whichever type of fuse plug is operatively seated in the base receptacle.

It is, moreover, my purpose and object generally to improve the structure, efficiency and adapting qualities of adapters oi the general type which screw into a standard Edison base cut-out receptacle for tamper-resisting purposes.

In the accompanying drawing:

Fig. 1 is a medial cross-sectional view through a standard Edison base cut-out receptacle having one type of fuse plug operatively mounted therein without any adapting means in the base receptacle;

Fig. 2 is an elevational view of an adapter, embodying features of the invention, which is mountable in the base receptacle of Fig. 1;

Fig. 3 is a medial cross-sectional view approximately on line 3-3 of Fig. 2;

Fig. 4 is a cross-sectional View of the socket portion of the base receptacle of Fig. 1. showing my improved adapter of Figs. 2 and 3 mounted therein and having' the fuse plug of Fig. 1 mounted therein;

Fig. 5 is a view similar to Fig. 4 but showing in elevation a so-called type S fuse plug assoe ciated with my improved adapter in the base receptacle;

Fig. 6 is a view similar to Fig. 5 but showing portions of the fuse plug in medial cross-section;

Fig. 7 shows the base receptacle of the earlier views with another modied form of adapter therein; and

Fig. 8 is a View similar to Fig. 7 but embodying still another modified form of adapter.

Referring to the drawing, the cut-out base indicated generally at I may be of any suitable design and construction but a conventional standard Edison cut-out base is illustrated, having the screw shell contact I2 electrically connected to the terminal element I4 to which a line conductor may be connected by means of the binding screw I6. The usual center contact of the base receptacle is indicated at I8 electrically connected to terminal element 28 which is adapted for connection to another line conductor by the binding screw 22.

My improved adapter comprises the generally tubular sleeve 24 of insulating material, which may be of Bakelite, for example, and it is a feature of the invention that an axial hole or passage 28, extending completely through the sleeve, has diameter for accommodating the center-contact-carrying portion 28 of a fuse plug of the type and design shown in Figs. 1 and 4, so that the center contact 3D on the end of said portion 28 may be passed through hole 28 into direct engagement with the center contact I8 of the base receptacle. Hole or passage 26 is threaded as at 32 so that it also can accommodate the exteriorly threaded center-contact-carrying portion 34 of a fuse plug of the diierent type and design shown in Figs. 9, with the said threaded portion 34 adapted to screw into hole 26 until its center contact 3S has been engaged directly with the center contact I8 of the base receptacle.

The insulating body of adapter sleeve 24 has exterior dimensions at one end portion thereof appreciably greater than the exterior dimensions of the main extent of the sleeve. and the exterior end DOrtion as at 52 of the sleeve is formed with threads from end to end thereof which have appreciably greater circumference at the said end portion of the sleeve which has the greater exterior dimensions as compared with the threads at the main extent of the sleeve. A metallic screw shell 38, or the like, is screwed on the insulating sleeve 24 with an inwardly extending annular flange 40 at one end for engaging the smaller end of the insulating sleeve, and with any suitable means at the other end, such as the swaged edge 42, for maintaining shell 38 permanently on the sleeve. This provides an exterior metallic threaded surface from end to end of the sleeve, and the threads at said greater dimension end portion of the sleeve are adapted to threadedly engage the screw shell contact I2 of the base receptacle when the adapter is screwed into the screw shell contact I2 with said larger end portion thereof leading. as clearly illustrated in Figs. 4 5. The smaller circumference threads on the main extent of the adapter are slightly spaced from the screw shell contact I2 as clearly seen at 44 in Figs. 4, 5 and 6, and this narrow space at 44 is adapted to accommodate the screw shell contact 48 of a fuse plug of the Figs. 1 and 4 type when one of them is screwed into the screw shell contact I2 of the base receptacle, as illustrated in Fig. 4. In Fig. 4, it will be obvious that the screw shell contact 4B of the fuse plug is electrically connected to the screw shell contact I2 of the base receptacle by reason of its direct engagement therewith, and also by reason of its direct engagement with the screw shell surface 38 of the adapter sleeve which electrically engages the screw shell contact I2 at its larger dimensioned inner end portion.

Referring now to Figs. 5 and 6, a so-called type S fuse plug is shown operatively mounted in the same adapter. In this case, however, there is no screw shell contact on the fuse plug but only the spring contacts 48 on the fuse plug through which electrical engagement with the screw shell contact I2 of the base receptacle must be effected. Hence, the threaded center-contactcarrying portion 34 of this type S fuse plug screws directly into the adapter as previously explained, thereby to bring its center contact 36 into direct engagement with the center contact I8 of the base receptacle. As the fuse plug is screwed into the adapter, the spring contacts 48 on the fuse plug resiliently engage the flange portion 40 of the screw shell exterior surface 38 of the adapter sleeve 24, thereby to eiect electrical engagement with the surface shell 38 and through it with the screw shell contact I2 of the base receptacle, at the larger dimensioned inner end portion of the adapter.

From the foregoing description, in connection with the drawing, it will be apparent that my improved adapter can inter-changeably accommodate fuse plugs of the Figs. 1 and 4 type and of the Figs. 5 and 6 type, and effectively coacts with either type oi fuse plug toprovide al desired highdegree of protection against fuse-tampering, and to provide so that either type of fuse plug projects out of a base receptacle substantially the same distance as a conventional fusev plug.

Figs. 7 and 3 illustrate modified forms of'- adapters which avoid the need for any metallic screw shell on the adapter insulating sleeves. In Fig. 7, the adapter insulating sleeve 5U, Without any metal shell, is exteriorly threaded at its inner for threaded engagement with the screw shell I2 `of the base receptacle, and has the smaller circumference threads 54 on the main portion of its extent slightly spaced from the screw shell contact I2 to provide the space 56 for reception of the screw shell contact 46 oi a fuse plug of the Figs. 1 and 4 type. The outer end portion of the adapter sleeve 50, however, is shown bevelled at 5S to provide an annular knife edge which is adapted to engage inside the spring contacts 48 of a type S fuse plug when one oi the latter is being screwed into the adapter sleeve 5D. By reference to Fig. 6, it will be seen that the spring contacts 48 of a type rS fuse plug are located on the plug body relatively close to the threaded portion 34 thereof and not in positions where they normally could be brought into direct engagement with the screw shell. contact I2 of the base receptacle. According to the invention, the inclined surface at the bevel 58 resiliently cams the contacts 48 edgewise outward enough so that the contacts directly engage the outer edge of the screw shell contact I2 before the center contacts 36, I8 directly engage each other.

In the Fig. 8 form thc bevel 58 is such as to cam the contacts 48 resiliently into edgewise ensagement with the interior surface of the screw shell contact I2.

The adapters of Figs. 7 and 8 can accommodate the Figs. l and 4 type fuse plug generally the same as shown in Fig.f4- but without the metallic screw shell on the adapter of Fig. 4. And, in every case where an adapter is not in the base receptacle, a fuse plug of the Figs. 1 and 4 type may be operatively mounted in the base receptacle the same as a conventional fuse plug.

In Fig. l, the fuse plug is shown equipped with a conventional fuse link BIJ electrically connected at one end to the center contact 30 and at its other end to the screw shell contact 46, while the type S fuse plug as shown in Fig. 6 has its fuse link 62 connected at one end by low melting temperature solder 64 and connected at its other end by high melting temperature solder E6, with a spring 68 for breaking the connection at 64 when the low melting temperature solder melts in response to a moderate overload of predetermined character. Obviously, the Fig. 1 fuse plug may have embodied therein a mechanical cut-out means comparable to that of the illustrated type S fuse plug, and the type S fuse plug may have only a simple fuse link comparable tov that of the Fig. l fuse plug.

Preferably, each of the illustrated forms of adapter will have means for making it diiicult to remove an adapter from a base receptacle once it has been embodied therein. A conventional form of such means is illustrated in Fig. 2, comprising the resilient wire 10 projecting outward through an opening 'I2 in the metallic shell 38 ci the adapter, close to the inner end thereof, in the Figs. 2-6 form, or anchored at its inner end in a comparable recess in the Figs. 7 and 8 form. In each case, the wire projects in a manner to have the outer end of the wire lagging and engaging the screw shell contact of the base receptacle when the adapter is being screwed into a base receptacle, so tends to dig into the screw shell contact when attempt is made to unscrew the adapter.

I claim as my invention:

1. In. a fuse plug base receptacle, a tamperresisting sleeve element having an axial passage therethrough substantially larger in diameter than the diameter of the center contact of the that the end of the wire base receptacle whereby the inner end of the sleeve surrounds the center contact of the base receptacle with the said center contact within the said passage, said sleeve engaging the screw shell contact oi the base receptacle only at an inner end portion thereof, and the Walls of said axial passage being threaded for reception` of a threaded center-contact-carrying portion of one type of fuse plug whereby the center contact of the fuse plug may be projected through said axial passage into direct engagement with `the center contact of the base receptacle, and said sleeve having means thereon for effecting electrical connection between a resilient contact ele-i ment of said one type of fuse plug and the screw shell contact of the base receptacle only at one end portion of the latter, there being an annular space between an outer portion of the sleeve and the screw shellcontact of the base receptacle for reception of a screw shell contact oi another type of fuse plug which may be screwed directly into the screw shell contact of the base receptacley thereby to project its center contact through said axial passage into direct engagement with said center contact of the base receptacle.

2. In a fuse plug base receptacle, a tamperresisting sleeve element having an axial passage therethrough substantially larger in diameter than the diameter of the center contact of the base receptacle whereby the inner end of the sleeve surrounds the center contact of the base receptacle with the said center contact within the said passage, a metallic shell on the sleeve having screw threads engaging the screw shell contact oi the base receptacle only at the inner end portion of the latter, said metallic shell extending in spaced relation to the screw shell contact of the base receptacle outward of its said engagement therewith, the walls of said axial passage being threaded for reception of a threaded center-contact-carrying portion of one type of fuse plug, whereby the center contact of the fuse plug may be projected through said axial passage into direct engagement with the center contact of the base receptacle, an outer part of said metallic shell on the sleeve being arranged for engaging a resilient contact element on said one type of fuse plug while the said spaced relation of the outward extending portion of the said metallic shell, relative to the screw shell contact of the base receptacle, provides an annular space for reception of a screw shell contact of another type of fuse plug which may be screwed directly into the screw shell contact oi' the base receptacle, thereby to project its center contact through said axial passage into direct engagement with the center contact of the base receptacle.

3. In a fuse plug base receptacle, a tamperresisting sleeve element having a threaded axial passage therethrough and having a metallic exterior shell threadedly engaging the screw shell contact of the base receptacle only at the inner end portion of the latter, said metallic shell extending as an electrical conductor in spaced relation to the screw shell contact of the base receptacle from said engaged inner end portion of the latter to an outer portion of the sleeve where it stands spaced from the screw shell terminal of the base receptacle in position to be engaged by a resilient contact element of one type of fuse plug when a threaded center-contact-carrying portion of said one type of ruse plug is screwed into said axial passage to project its center contact into direct engagement with the center contact of the base receptacle, the said spaced relation of the outer portions of the metallic shell on the sleeve and the screw shell contact oi the base receptacle providing an annular space for reception of a screw shell contact of another type of fuse plug which may be screwed directly into the screw shell contact of the base receptacle to project its center contact through said axial passage into direct engagement with the center contact of the base receptacle.

4. In a fuse plug base receptacle, a tamperresisting sleeve element having a threaded axial passage therethrough for reception of a threaded center-contact-carrying portion of one type oi fuse plug and having exterior means engaging the screw shell contact of the base receptacle only at the inner end portion thereof, whereby the outer end portion of the sleeve element is adapted to enter within a screw shell contact of a different type of fuse plug when said screw shell contact of said different type of fuse plug is screwed directly into the screw shell contact of the base receptacle, the center-contactcarrying portion of each of said two types of fuse plugs fitting said axial passage for selective projection of the center contact of a fuse plug of either type into direct engagement with the center contact of the base receptacle in response to rotation of a plug of either type relative to the sleeve element, said sleeve element having a metallic shell thereon, and said exterior means on the sleeve element which engages only the inner end portion of the screw shell contact of the base receptacle being on the said metallic shell, said metallic shell extending outward from said engagement in spaced relation to the screw shell Contact oi the base receptacle and constituting a conducting connector between said engaged inner end portion of the screw shell Contact of the base receptacle and a contact element on one of said types of fuse plug, and serving as a conductor in parallel with the screw shell contact of the base receptacle when the screw shell contact of said different type of fuse plug is screwed directly into the screw shell Contact of the base receptacle.

WILLIAM S. EDSALL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Germany Sept. 15, 1900 Number Number 

